Benchmarking GE-BOLD, SE-BOLD, and SS-SI-VASO sequences for depth-dependent separation of feedforward and feedback signals in high-field MRI

Abstract

AbstractRecent advances in high-field fMRI have allowed differentiating feedforward and feedback information in the grey matter of the human brain. For continued progress in this endeavor, it is critical to understand how MRI data acquisition parameters impact the read-out of information from laminar response profiles. Here, we benchmarked three different MR-sequences at 7T - gradient-echo (GE), spin-echo (SE) and vascular space occupancy imaging (VASO) - in differentiating feedforward and feedback signals in human early visual cortex (V1). The experiment (N=4) consisted of two complementary tasks: a perception task that predominantly evokes feedforward signals and a working memory task that relies on feedback signals. In the perception task, participants saw flickering oriented gratings while detecting orthogonal color-changes. In the working memory task, participants memorized the precise orientation of a grating. We used multivariate pattern analysis to read out the perceived (feedforward) and memorized (feedback) grating orientation from neural signals across cortical depth. Analyses across all the MR-sequences revealed perception signals predominantly in the middle cortical compartment of area V1 and working memory signals in the deep compartment. Despite an overall consistency across sequences, SE-EPI was the only sequence where both feedforward and feedback information were differently pronounced across cortical depth in a statistically robust way. We therefore suggest that in the context of a typical cognitive neuroscience experiment as the one benchmarked here, SE-EPI may provide a favorable trade-off between spatial specificity and signal sensitivity.HighlightsHere, we benchmarked three sequences at high-field fMRI -GE-BOLD, SE-BOLD and VASO - in differentiating feedforward and feedback signals across grey matter depth of area V1. We show that:All the MR-sequences revealed the feedforward and feedback signals at the middle and deep cortical bins, respectively.Such correspondence across the sequences indicates that widely used GE-BOLD is a suitable method for the exploration of signals in cortical depth.Only SE-BOLD yielded statistically reliable differences between the cortical bins carry- ing feedforward and feedback signals.